Tanker with membrane tanks for carrying low temperature liquified gas

ABSTRACT

A tanker for transporting low-temperature liquified gases having a tank structure therein constructed separately therefrom. The tank structure is disposed within the hold space and is constructed with a rigid exterior outer vessel having an inner membrane tank for storing low-temperature liquified gases. The inner tank is constructed as a flexible inner fluid-container vessel made of a thin metallic membrane. The tank structure is constructed independently of the ship itself and then is inserted into the ship structure or hold thereof.

United States Patent [191 Yamamoto [111 3,820,492 June 28, 1974 TANKER WITH MEMBRANE TANKS FOR CARRYING LOW-TEMPERATURE LIQUIFIED GAS [75] Inventor: Katsuro Yamamoto, Tokyo, Japan [73] Assignee: Bridgestone Liquefied Gas Company Limited, Tokyo, Japan [22] Filed: Dec. 29, 1972 [21] Appl. o.5 319,153

[30] Foreign Application Priority Data Dec. 28, 1971 Japan; 46-868 [52] us. Cl i. 114/74 A, 220/9 LG [51] Int. Cl B63b 25/08, B65d 25/18 [58] Field of Search 1 14/74 .R, 74 A, 74 T;

220/9 LG, 9 A, 9 F

[56] References Cited UNITED STATES PATENTS 3,071,094 1/1963 Leroux 1l4/74A 3,613,932 10/1971 Yamamoto ..220/9 LG 3,622,030 11/1971 Yamamoto 114/74A Primary Examiner-Trygve M. Blix Assistant Examiner-Charles E. Frankfort Attorney, Agent, or Firm-Robert E. Burns; Emmanuel J. Lobato; Bruce L. Adams ABSTRACT 6 Claims, 1 Drawing Figure BACKGROUND OF THE INVENTION Containers and tankers for carrying and storing lowtemperature liquified gases are known. In these tankers, the container for these gases is constructed as a thin membrane tank placed inside the hold surrounded by a pressure-resisting structure which is also heatinsulating. The thin membrane tank is made of thin steel sheets, or other suitable material, which will deform under the influence of the internal pressure thereby coming into close contact with the surface of the heat-insulating layer. Because of this added structure and space requirement for a given capacity, the tankers so constructed must have a larger hull as compared with the capacity of the inner vessel, because of the need to encase the inner vessel within the hull. This has resulted in increased costs in the construction of tankers for carrying the low-temperature liquids.

SUMMARY OF THE INVENTION It is an object of the'present invention to provide a tanker construction which eliminates the drawbacks inherent to conventional tanker construction.

Another object of the invention is to provide a tanker with an independently constructed tank structure which markedly reduces the dimensions of the tanker according to the invention.

Another object of the present invention is to provide a tanker ,for transporting low-temperature liquified gases having a lower center of gravity and thereby higher stability than tankers of other types.

The tanker according to the invention has a hull in which a tank structure constructed independently of the hull is disposed independently of the hull. The tank structure comprises a rigid outer vessel having inner and outer bottoms, inner and outer side walls, and an inner and outer top structure. A heat-insulating layer is disposed in this outer vessel between the bottoms, side v walls, and top structures. Within the outer vessel is provided an inner flexible, fluid-containing vessel or tank having'a bottom, side walls, and a top made of afluidimpervious metallic material. This material is constructed as a thin metallic membrane.

The inner tank or vessel has a deformablemarginal portion in the area of juncture of the top and side walls thereof, and a deformable marginal portion in the area of junction of the sidewalls and bottom. Both of these marginal portions have a convex configuration arcuate in cross section, and both extend peripherally of the top and bottom. The top has a central opening in registry with a trunk in the top structure of the outer rigid vessel and communicating therewith. The marginal portion of the top of the inner vessel is secured to the top structure of therigid outer vessel. The heat-insulating layer of the outervessel is compression-resistant and is configured to receive the inner tank.

The tanker itself is provided with cradles for revealing the tank structure which is slung into position in the hold of the hull of the tanker after being constructed separatelyfrom the tanker hull.

BRIEF DESCRIPTION OF THE DRAWING. The illustrated embodiment of theinvcntion is a fragmentary vertical cross-section view of a tanker provided with a tank structure in accordance with the principles of the instant invention.

Other objects and advantages of the tanker and tank structure will appear from the following description of an example of the present invention; and the novel features will be particularly pointed out in the appended claims.

DESCRIPTION OF THE PREFERRED EMBODIMENT A tanker in accordance with the present invention is fragmentarily shown in the drawing and has a double hull 1. Within the hull is provided a separate tank structure having a heat-insulating layer 2 for insulating a thin membrane inner vessel or tank 3 contained within the rigid outer tank box-like structure tank 4 exteriorly of the heat-insulating layer 2. The outer tank structure 4, inner heat-insulating layer 2, and the inner membrane tank 3 constitute a tank structure 5 which is constructed independently of the hull l of the vessel or tanker.

The inner membrane tank or vessel 3 is made of thin sheets of low-temperature resisting material such as nickel, stainless steel or aluminum ranging in thickness from about three to six millimeters. The outer tank structure is provided with a rigid trunk 6 about which the sheet-insulating material is likewise disposed, and it is joined to a rigid curver 4" of the tank structure by heat-insulating member 7.

The inner tank 3 is constructed with side walls 3 joined to a bottom 3" thereof along an area of juncture which is convex and arcuate in configuration and cross section and extends peripherally of the bottom. The side walls are 3' joined to a top 3a along an area of juncture 3b that is convex and is arcuate in cross section and circumferentially about the top of the tank.

The top wall 3a of the inner tank is supported so that it does not sag down or is supported on the underside thereof if necessary by means, not shown, or by connection to a flange 8 of the trunk 6. The trunk 6 is covered as illustrated and through this cover suitable pipes, not shown, for loading and'unloading the liquid gas extend into the .interior of the inner vessel or tank.

The curved area 3b in the area of juncture of the top and side walls provides a means of absorbing expansion and contraction of the inner vessel occurring with changes in temperature and accordingly this curved arcuate area is not restrained, but is supported internally by the pressure P applied by the liquid gas. This area is also capable of maintaining its arcuate shape even when the internal pressure of the liquid in the vessel is not operating on it and this is accomplished due to the rigidity imparted by the curvature of its shape.

Within the box-like steel outer structure 4 is installed a secondary wall 4a, made of board or some other material with a space being left therebetween and a wooden frame, not shown, connects the box-like supporting structure 4 and the secondary wall 40. The heat-insulating material 2 fills the space or cavity between the secondary inner wall and the outer wall of the outer tank structure and is preferably compressionresistant, for example rigid foamed polyurethane, pearlite in powder or grain form, glass wool or some other material imparting a compression resistance to the-entire frame structure.

The box-like supporting structure 4 has a bottom 4 and side walls 4" made of relatively thin steel sheets and capable of maintaining the shape of the entire structure but incapable of supporting the internal pressure of the inner vessel. The top wall 4' of the structure is capable of fully supporting the internal pressure of the inner vessel and may be used to sling the tank structure 5 into the hold space of the tanker after it is constructed.

The tank structure 5 consisting of the inner vessel 3 and the supporting structure 4 spaced by the heatinsulating layer 2 is constructed independently of the ship and then placed inside of the hull of the tanker. The tank structure 5 is constructed so that an area of juncture 3c of the curved area 3b to the side walls 3' is substantially at the level of the upper or main deck 1a of the tanker. An upper section U of the tank structure 5 above the main deck projects from the hull and the hull is provided with a rigid structure for securing to the main deck and to support the inner pressure. The lower section of the tank structure is located below the main deck and encased in the hull so that the pressure which acts on the side walls 3' and bottom 3" of the inner vessel in a low-temperature loaded condition is supported by the hull of the tanker. On the other hand, the curved shoulder portion 3b of the inner vessel which is not in contact with the internal surface of the secondary or inner wall 4a inside the heat-insulating layer 2 and the upper surface U of the tank structure is fully capable of supporting the internal pressure P of the inner vessel in view of its curved construction and hoop tension. Thus it is possible to maintain the shape design of the tank structure and the hull as desired. The structure according to the invention can thus be achieved without providing any joints or points of juncture between the tank and the hull, thereby facilitating installation of the tank structure to the tank or hull.

In order to prevent movement of the tank structure due to rocking and rolling of the ship, the tank structure is firmly fitted to the hull by saddle members 9 which have been previously placed at the bottom corners of the supporting structure 4 within the hull. The upper structure U of the tank structure is firmly fixed to the upper deck la by means of supporting members 10, whereby the tank structure 5 is kept stable inside the hull.

If any space is left between the hull l and the tank structure 5, when it has been installed in the tanker filling material such as a polymer cement or resin filler can be filled in. This filling material will not only increase the strength of the tank structure, but also permit efiicient construction of the tank structureitself In the construction illustrated, the loading pipes and other machinery and other equipment may be mounted on the top wall 4' of the supporting structure serving as a rigid cover prior to the installation of the tank structure 5 in the hull 1. This offers various advantages in that the time required for outfitting can be greatly shortened and in that the upper section U and the top structure is not covered by the hull which permits not only access to the tank structure outside, but also the installation of inspection points. This facilitates maintenance as compared with the conventional arrangement in which the membrane tank is installed completely below the upper or main deck.

Thus it can be seen that the invention provides a lowtemperature liquified gas tank construction which saves in materials and lowers materially construction costs while increasing the stability of the vessel as well as increasing tank capacity.

What I claim and desire to secure by Letters Patent l. A tanker having a hull and a main deck, a tank structure disposed within said hull and independent thereof for storing a low-temperature liquefied gas, said tank structure comprising a rigid outer vessel having inner and outer bottoms, inner and outer side walls and an inner and outer top structure, a heat-insulating layer in said vessel between the bottoms, side walls and top structures, a flexible, inner fluid-containing vessel internally of said rigid outer vessel and having a bottom, side walls and a top made of a fluid impervious metallic material, said inner vessel top having a deformable, marginal portion in the area of juncture of the top and side walls thereof, said portion having a convex configuration arcuate in cross section, the arcuate marginal portion extending peripherally of said top, said top having a central opening, a trunk in the top structure of said outer rigid vessel in communication with said opening, means securing to said top structure a marginal portion of said top of the inner vessel bounding 'said central opening, said heat-insulating layer including heat-insulating material over said top of the inner vessel, said inner vessel having a deformable, marginal section portion in the area of juncture of the side walls and said bottom thereof, said second portion having a convex configuration arcuate in cross section a the area of juncture and extending circumferentially of the inner vessel, said marginal portion in the area of juncture of the top and side walls of said inner vessel being disposed at a level in the vicinity of the level of a main deck of the hull, and means securing said tank structure to the hull above the level of the main deck.

2. A tanker according to claim 1, in which said inner vessel is made of a thin metallic membrane.

3. A tanker according to claim 1, in which said heatinsulating layer material comprises a compressionresistant material.

4. A tanker according to claim 3, in which said compression-resistant material is rigid foamed polyurethane.

5. A tanker according to claim 1, including saddle means at the bottom of said outer rigid vessel holding the tank structure in said hull.

6. A tanker according to claim 1, in which said outer vessel comprises a rigid, convex marginal portion arcuate in cross section in an area of juncture of the outer side walls and outer bottom thereof extending circumferentially thereof. 

1. A tanker having a hull and a main deck, a tank structure disposed within said hull and independent thereof for storing a low-temperature liquefied gas, said tank structure comprising a rigid outer vessel having inner and outer bottoms, inner and outer side walls and an inner and outer top structure, a heatinsulating layer in said vessel between the bottoms, side walls and top structures, a flexible, inner fluid-containing vessel internally of said rigid outer vessel and having a bottom, side walls and a tOp made of a fluid impervious metallic material, said inner vessel top having a deformable, marginal portion in the area of juncture of the top and side walls thereof, said portion having a convex configuration arcuate in cross section, the arcuate marginal portion extending peripherally of said top, said top having a central opening, a trunk in the top structure of said outer rigid vessel in communication with said opening, means securing to said top structure a marginal portion of said top of the inner vessel bounding said central opening, said heatinsulating layer including heat-insulating material over said top of the inner vessel, said inner vessel having a deformable, marginal section portion in the area of juncture of the side walls and said bottom thereof, said second portion having a convex configuration arcuate in cross section a the area of juncture and extending circumferentially of the inner vessel, said marginal portion in the area of juncture of the top and side walls of said inner vessel being disposed at a level in the vicinity of the level of a main deck of the hull, and means securing said tank structure to the hull above the level of the main deck.
 2. A tanker according to claim 1, in which said inner vessel is made of a thin metallic membrane.
 3. A tanker according to claim 1, in which said heat-insulating layer material comprises a compression-resistant material.
 4. A tanker according to claim 3, in which said compression-resistant material is rigid foamed polyurethane.
 5. A tanker according to claim 1, including saddle means at the bottom of said outer rigid vessel holding the tank structure in said hull.
 6. A tanker according to claim 1, in which said outer vessel comprises a rigid, convex marginal portion arcuate in cross section in an area of juncture of the outer side walls and outer bottom thereof extending circumferentially thereof. 